//// 索引查询类型：用于查询属性的类型
// 定义属性集合
type Props207 = {a: number; b: number; c: boolean} 

// 查询属性
type Type207 = Props207['a']


//// 模拟partial类型
type MyPartial<T> = {
    [P in keyof T]?: T[P];
};



// 多属性查询
type Props207New = {a: number; b: string; c: boolean; d: undefined; e: symbol; f: bigint} 
type Type2071 = Props207New['a'|'b'] // number | string
type Type2072 = Props207New[keyof Props207New]  // number | string | boolean | undefined | symbol | bigint 